In general, content distributor devices (e.g., radio transmitters, cellular wireless transmitters) transmit audio, images, or text, (e.g., content or content messages) to end user or receiver devices (e.g., radio receivers, cellular wireless receivers) using a variety of distribution mechanisms.
One conventional mechanism for content distribution involves broadcast transmission of content. In broadcast transmission, such as radio or satellite broadcast, a single content source transmits content to many receivers (one-to-many transmission). Certain broadcast transmissions, such as shared-medium broadcasts or Code-Division Multiple Access (CDMA) transmissions, for example, utilize spread-spectrum techniques in broadcasting the content. Spread-spectrum is a modulation technique that uses a pseudo-noise (PN) code sequence to “spread” a signal over multiple frequencies within a channel for transmission (e.g., broadcast) to a receiver device. For example, a transmission device combines an input signal with a user-specific pseudo-noise code and transmits the combined signal to a receiver device. The receiver device locally produces a correlated signal by generating the same PN code sequence and synchronizing its code sequence with that of the received code sequence. The receiver device, therefore, tracks the received encoded signal to recover the input signal.
The spread-spectrum technique provides security to a signal transmitted to a receiver device. For example, the spread-spectrum technique provides antijam capabilities to the transmitted signal. In spread-spectrum, the transmitter transmits the signal, to a receiver device, using several frequencies. In such a transmission, an unauthorized user can have difficulty in distinguishing the signal from noise. The spread-spectrum technique, therefore, limits the ability for an unauthorized user to “jam” or inject noise within the transmission.
The spread-spectrum technique, furthermore, provides low probability of interception (LPI) capabilities to the transmitted signal. For example, when using the spread-spectrum technique, the transmitter device transmits a signal to a receiver device using several frequencies. In such a transmission, an unauthorized user can have difficulty in retrieving the complete signal from the transmitter device. The spread spectrum technique, therefore, minimizes interception of the transmitted signal.
Another conventional mechanism for content distribution involves multicast transmission. In multicast transmission, such as Internet Protocol (IP) multicast or application-level multicast, a content source transmits content to many receivers (e.g., one-to-many) using a multicast-enabled network. For example, assume a content source (e.g., content server) receives, over a computer network, requests for content from multiple requesting devices (e.g., client devices). The content source provides content to the network in response to the content requests. In multicast transmission, multicast-enabled data communications devices within the network distribute the content to all of the multiple requesting devices. The content source, therefore, provides the requested content to the network once and allows the multicast-enabled data communications devices within the network to distribute the content to the requesting devices. Multicast distribution of content over the network limits loading of a particular content source with the task of providing, for multiple iterations, identical content to multiple requesting devices, thereby allows for a more efficient operation of the content source.